1. Field of the Invention
This invention relates to tow cables for underwater applications and more particularly to a termination device and a method for terminating braided ropes or cables of aramid fiber to increase the reliability of such cables.
2. State of Prior Art
As described in U.S. Pat. No. 4,184,784 to Killian the introduction of aramid fibers having great tensile strength has made possible a number of applications for lightweight high strength cables for underwater applications and arrays. The major advantage of using aramid cables is that they are light-weight compared to cables made of steel and provide extra strength. It is to be noted that such cables have been marketed under the trade name "KEVLAR" which is a trademark of Dupont Corporation and they require special handling. One of the characteristics of aramid fibers is that they retain their tensile strength right up to the breaking point. Consequently, it has been found to be a very difficult problem to provide a satisfactory termination for such cables since any significant variation in strand length causes the load to be carried to the shortest length strand until it breaks and then the load being transferred to the next available shortest piece, etc. with each strand failing under load until all are broken. It is thus quite important that terminating a cable or rope of KEVLAR is done carefully to maximize the strength of the rope at termination. Various techniques have been used in the prior art with limited success. As an example, Killian, as described in U.S. Pat. No. 4,184,784 which is incorporated herein by reference, uses a tapered coupling having a central sleeve passing through the axis of that coupling. KEVLAR strands or braids or fibers are passed through the annular space between the coupling and the central sleeve and a wedge is inserted from the opposite end to secure the position of the KEVLAR cable after it has passed through the sleeve. However, it has been reported that the results obtained with the termination procedure described and claimed in the above mentioned patent to Killian meets partial success in that the strength of the termination of the KEVLAR cable is up to about 50% to 70% of its original strength. There is thus still a need to improve the termination device and a terminating procedure so as to improve the strength of the cable up to its normal strength at the termination point.